string[] arr = s.Split (',');

Dictionary<string, int> Statistics = new Dictionary<string, int>();

foreach (string w in arr)
{
if (Statistics.ContainsKey(w))
{
Statistics[w] += 1;
}
else
{
Statistics[w] = 1;
}
}

<asp:Repeater ID="Repeater1" runat="server">
<HeaderTemplate>
<table border="1" cellpadding="1" cellspacing="0">
<tr>
<td>字符 </td>
<td>次數 </td>
</tr>
</HeaderTemplate>
<ItemTemplate>
<tr>
<td>
<%# Eval("key") %>
</td>
<td>
<%# Eval("value") %>
</td>
</tr>
</ItemTemplate>
<FooterTemplate>
</table>
</FooterTemplate>
</asp:Repeater>

protected void Page_Load(object sender, EventArgs e)
{
this.Repeater1.DataSource = Statistics;
this.Repeater1.DataBind();
}